(1) Field of the Invention
The present invention relates to a fluid flow regulating valve, and more particularly, to a fluid flow regulating valve using thermal expansion material which can precisely regulate the flow of large and small amounts of fluid.
(2) Description of the Related Art
A conventional flow regulating valve using thermal material is disclosed in U.S. Pat. No. 4,943,032. Reference to FIG. 10 will be made to describe this patent.
The flow regulating valve comprises a first silicon wafer 12, a Pyrex wafer 22 attached on an upper side of the first silicon wafer 12, and a second silicon wafer 30 attached on a lower side of the first silicon wafer 12. A chamber 10 for receiving thermal expansion material is etched in the first silicon wafer 12 and a cavity 21 for receiving a heater 21 is etched in an area between the chamber 10 and the Pyrex wafer 22. A thickness (h) of an area 12a between the first silicon wafer 12 and the chamber 10 etched therein is extremely thin to where it is only a few .mu.m. Also, a slot 44 for allowing flow of fluid is formed in an area where the first silicon wafer 12 and the second silicon wafer 30 are attached, and a nozzle 32 is etched in the second silicon wafer 30 at a location next to the area 12a under the chamber 10.
With regard to the operation of the above fluid regulator, when light is supplied to the Pyrex wafer 22 through a light pipe 19 or when the heater 21 is operated, the material contained in the chamber 10 expands. This acts to expand the area 12a of the first silicon wafer 12, as it is the thinnest part thereof, in a direction toward the nozzle 32. As a result, fluid entering through an inlet port 46 then sent to the nozzle 32 through the slot 44 is regulated according to the degree of expansion of the area 12a under the chamber 10.
In the above prior art valve, the heater 21, the chamber 10, and the slot 44 are either etched or go through a microscopic silicon process such as a photographic process. However, these processes require the use of very expensive equipment.
Also, the microscopic silicon process is a technique used for valves that regulate only a small flow of fluid. Valves manufactured by this process are used in medical instruments, environmental analysis instruments and the like. As a result, the application of valves made using this process is limited.
In addition, to regulate a large flow of fluid, the capacity of both the silicon wafer and the Pyrex wafer for each valve should be enlarged. However, this greatly increases manufacturing costs.
Furthermore, since diameters of inlet and outlet ports and a slot are processed having minute dimensions, foreign substances contained in fluid can easily block passages, deteriorating the reliability of the products.